Bone loss is a major, frequent and often permanent comorbid medical complication of anorexia nervosa (AN) affecting over half of all women with this disease and resulting in debilitating fractures, yet there are few effective therapies. In this proposal, we will test the effectiveness of a sequential therapeutic regimen designed to specifically: 1) reverse insulin-like growth factor 1 deficiency, thereby stimulating bone formation, and 2) reduce bone breakdown, using a bisphosphonate, a medication that is effective at reversing bone loss.